What is the difference between 304 and 430 stainless steel？

What is the difference between 304 and 430 stainless steel？

Stainless steel is an alloy of steel with vast industrial and domestic applications, and has several variants/grade. In this article, we examine grade 304 and 430.

Grade 304 and 430 are common grades of stainless steel with similarity in physical appearance but there are still some marked differences between them. Before we talk about these differences, let’s quickly examine what Stainless steel is.

Stainless steel

Stainless steel is an alloy containing iron carbon, and chromium mainly. As a rule, the chromium composition must be minimum of 10% for it to be regarded as stainless steel.

Stainless steel grades

Apart from the Carbon, Iron, and Chromium content, stainless steel may contain other chemical constituents that alter its properties, this gives rise to grading. The grading of stainless steel is very important in the industry as it helps to maintain industry standards and provide better quality steel.

Classification of Stainless Steel Grades

Usually, stainless steel is classified into different grades by various steel standard organizations across the globe. These organizations define the parameters that classify steel into different grades. With many organizations or agencies across the globe involved in the classification of steel, this classification does not have a gold standard. Therefore, different countries may set up grade parameters that are different. For example, 304 and 430 are exclusive to the AISI ( American Iron and Steel Institute)

Brief description of the  430 stainless steel?

This is a unique grade of steel classified by AISI as a fairly strong anti-corrosive stainless steel with excellent flexibility.

Composition

The following are the chemical composition of stainless steel 430

Iron -Same as other grades

Carbon – 0.12%

Chromium -Ranges between 16% -18%

Nickel -Less than 0.75%

Manganese- less than  1.0%

Silicon – less than  1.0%

Phosphorus – less than  0.040%

Sulfur less than 0.30%

It is important to point out that stainless steel 430 is unsuitable for welding due to the elevated carbon level which is higher when compared to other grades and the absence of stabilizing components.

Physical properties

Its yield strength is estimated to be about 30ksi

It has a tensile strength of about 65ksi

It has a density of 7.75g/cm³

Its melting point is between 1425-1510°c

It has a Modulus elasticity of 0.6 x10^-6

Application.

The most common application of this grade of stainless steel is in the cosmetic industry where aesthetics appeal is needed.

Brief description of the 304 stainless steel

It is a popular grade of stainless steel with a variety of applications in different industries, and its most useful application is in kitchen utensils.

Composition of 304 stainless steel

Its composition analysis is as follows

Iron- Normal

Carbon – between 0.0 – 0.07%

Chromium – between  17.50 – 19.50%

Manganese – between 0.0 – 2.0%

Silicon – between  0.0 – 1.0%

Phosphorous – between  0.0 – 0.05%

Sulfur – between  0.0 – 0.03%

Nickel – between 8.0 – 10.5%

Nitrogen – between 0.0 – 0.11%

Note that unlike 430, 304 can easily undergo welding due to its carbon composition (which is relatively lower than grade 430), and presence of stabilizing components

Physical property

It has a melting point of 1399 °C – 1454 °C

Its yield strength is estimated to be about 30ksi

It has a tensile strength of about 65ksi

It has a density of 7.75g/c 1425-1510°c

It has a Modulus elasticity of 0.6 x10^-6

Differences between 304 and 430

There are some marked differences between these two grades of steel. The differences include:

Nature of steel

One of the most significant differences between 430 and 304 is that Stainless steel 430 is ferritic while 304 is austenitic. Steels are generally classified into ferritic, austenitic, and martensitic.

Ferritic steels are steels that contain a lower proportion of Nickel which makes them easily magnetized and less expensive. These types of steels can easily be maser harder using the cold working technique

Austenitic steels are steels that have an increased proportion of Nickel which reduces its magnetic property and strengthens its corrosive property. They are the most common types of stainless steel.

Corrosion tendency

Stainless steels are generally resistant to corrosion, however, this property may vary from one grade to another.  Grade 304 due to its chemical composition has stronger corrosion resistance compared to 430. This is because in addition to Chromium which is in 430 and 304, 304 contains nickel which strengthens its corrosion property.

Magnetic grade

Grade 430 has a stronger magnetic property than 304 because 430 is a ferritic type of steel, and 304 is an austenitic grade of steel. This variation in magnetic properties is a result of the compositions of nickel in 304.

Hardness

Stainless steel 430 and 304 have different hardness. The hardness of stainless steel is usually measured using Brinell Hardness Number.  The greater the value the harder the steel. For this, 430 has a BHN of 183 while 304 is 201, meaning that 304 is harder than 430.

Use in the food industry

Grade 304 has more usefulness in the food industry than 430, this is because 304 is hygienic for use. Grade30 is rarely used in the food industry.

Demand

Different grades of steel have varying demands, however, 304 remains the most demanded grade of steel. It has more application than other grades of steel including 430. That said, 430 is the 2^nd most demanded grade of steel.

Cost

Even though 304 is more in demand, the cost of 304 is higher than that of 430. Grade 430 is most times used because of budget constraints.

Utility

304 and 430 have a varying utility that makes them suitable for different roles. 430 can with ease undergo bending and stretching but it is not easily welded.

While 304 on the other hand can be welded, pressed, and stretched with ease. This is because its carbon content.

Which is better 304 or 430

Well, 304 is more widely used than 430 but this does not mean it is more useful than 430. This is because they have unique role that cannot be substituted for each other. For example, 430 is suitable for the cosmetic industry while 304 has more use in kitchen utensils and food processing.

In conclusion, the choice of stainless steel grade would depend on the industry to be used in and the purpose of use.